Silicon photonics chips are being developed for high speed interconnects between dies. Waveguides can be built on SOI wafers and can be integrated with CMOS devices. In these structures, though, a connection must be made between an “off-chip” optical fiber and the waveguide. Out-of-plane coupling uses an optical grating to couple light from the fiber to the waveguide, but this limits the optical signal to one wavelength. In-plane coupling, on the other hand, allows broadband transmission (e.g., multiple wavelengths) and hence higher bandwidth.